The vertical stones -- over 10 feet tall and weighing many tons -- form the site that's believed to be nearly 5,000 years old. And nobody is sure why or how Stonehenge was originally built.

"This new survey will capture a lot more information on the subtleties of the monument and its surrounding landscape," said Paul Bryan of English Heritage, an adviser to the British government on historic buildings and monuments.

English Heritage is using both 3D laser scanning and digital imaging technology to survey every inch of every stone at Stonehenge. The end result should be the most accurate digital model ever created of the famous site.

Archaeologists have suggested a variety of reasons for the origin of Stonehenge, including its possible use as a burial ground or as a sophisticated astronomical observatory. Researchers have speculated that the huge stones were placed in precise positions to observe the heavens.

Others have suggested Stonehenge may have even been an ancient tourist destination used as a center of healing.

Adding to the mystery of Stonehenge has been the question of how the original builders transported the stone slabs over 150 miles from their quarry to the Salisbury Plain.

"The surfaces of the stones of Stonehenge hold fascinating clues to the past," said Dave Batchelor, an English Heritage archaeologist. "They are like manuscripts, a whole palimpsest of the ideas, efforts and idiosyncrasies that marked the lives of people over millennia.

"I look forward very much to seeing what we are about to find."

Researchers also hope their laser scans will shed light on so-called "rock art," carved pictures and modern graffiti embedded in some of the giant stones.

The last detailed survey of Stonehenge was done in 1993 using photogrammetry. "The 2-centimeter resolution that was possible back then will be surpassed by the millimetric resolution of this new survey, which will capture a lot more information on the subtleties of the monument and its surrounding landscape," Bryan said.

The laser survey of Stonehenge is under way and is expected to conclude at the end of this month.